This invention relates generally to numerical control systems for machine tools and more particularly to a computerized numerical control system there for.
Numerical control systems for controlling machine tools in accordance with the execution of stored programs in a digital computer are well known. Such systems control the motion of a machine tool in response to one or more part programs which are stored in a memory after having been loaded into the memory via a punched tape, for example. Upon demand the part program(s) stored thereafter directs the machine through a series of fabrication steps. Where, for example, the machine includes a cutting tool, the relative motion between the workpiece and the cutting tool is normally along three mutually perpendicular axes to make a series of straight line or circular cuts in accordance with a sequence of digital numbers which indicate where the cuts are to be made and their order.
In addition to controlling the axis motions between the cutting tool and the workpiece, numerical control systems are also adapted to control auxilary functions of the machine tool such as tool selection and changing, spindle speed, coolant flow and pallet selection. The number and type of auxiliary functions vary considerably depending upon the type of machine tool being controlled and typically have been performed in the past by separate hardware logic circuits which operate in response to both the sensed conditions on the machine tool and to commands indicated by the selected codes in the part program. More recently, however, programmable controllers have been interfaced with the numerical control system computer apparatus to control the auxiliary functions. Such programmable controllers can be either a separate program processor or an integral part of the numerical control system computer. The advent of a programmable control to a numerical control system provides a number of advantages, the first and foremost of which is that programmable controllers need not be changed when integrating the numerical control system to other types of machine tools. It is only necessary to reprogram the controller to enable it to interface with the particular machine at hand. Additionally, a programmable controller is relatively easier for the user to program because of the type of instruction set which is normally employed and the editing features which are normally available.